Method for selection of camera image sections

ABSTRACT

A method for monitoring the process in laser material processing and provides a corresponding method, comprising the steps of taking a real-time image comprising the position and surrounding of the process where material processing occurs by a camera that is arranged in or on a laser material processing head; determining at least one image section in the real-time image and its position on a camera sensor; determining an actual position of the process in the material processing, and a nominal position of the relevant image detail using a projection of programmed path data for controlling the laser material processing head in the section of the real-time image, and the transfer of the at least one image section from the camera to a computer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to German patent application DE10 2019 101 222.8, filed on Jan. 17, 2019. The aforementionedapplication is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates a process for monitoring the process of lasermaterial processing.

Brief Description of the Related Art

In laser material processing, image processing systems are used tocontrol the seam tracking. Digital image processing systems are alsoused for process control, regulation or control and quality assurance.

An essential task in the use of digital image processing is theselection of suitable images for the particular application. Forexample, when working on a part of a workpiece, an image must beselected that shows the relevant area of the edge that is to be machinedor whose processing is to be controlled. Selection criteria oriented tothe respective process are required for the selection of images or areasfrom a sequence of images.

In laser material processing, only a small portion of a camera image isusually required. By using suitable processes, the amount of data isreduced, which then also has an advantageous effect on the transmission,the required storage space and computational effort.

Published International application WO 2012/163545 A1 discloses a methodfor monitoring the machining of a workpiece with a high-intensitymachining beam. The method disclosed in this document comprises thefollowing steps: recording an electronically evaluable image containingat least the point of impact of the processing beam on the workpiece,generating actual image data, comparing the actual image data withtarget image data, generating an image error signal in case of adeviation of actual image data from the nominal image data, detectingthe actual process parameters controlling the processing to be monitoredsynchronously with the generation of the actual image data, comparingthe actual process parameters with nominal process parameters,generating a process error signal in the event of a deviation betweenthe actual process parameters and the nominal process parameters,generating an error signal in the simultaneous presence of an imageerror signal and a process error signal, and triggering measures in thepresence of an error signal. A disadvantage of the solution disclosed inthis document is that it relies on the availability of nominal imagedata.

Laser remote welding is a special variant of laser beam welding. In thismethod, welding can take place in any direction in a three-dimensionalspace and the direction can change during the welding process. This is adifference to other welding heads, which usually only weld in onedirection. In such devices detectors or guide elements are used, whichprecede the joining process.

Another significant advantage of the remote laser welding compared tothe laser beam welding is that it is possible by means of movablemirrors to jump much faster from one weld to another, so that the totalprocessing time of a workpiece can be significantly reduced. In remotelaser welding, therefore, the seam to be welded can theoretically beanywhere in the workspace.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to provide a method, inparticular for remote laser welding, enabling recording in a short timein three-dimensional space the relevant part of the workpiece. Thisrelevant part may be in a state

1. before the process, if e.g. seam tracking is intended;

2. after the process, if e.g. quality control is intended;

3. around the process, if e.g. process control is intended.

The present invention provides a method of monitoring the process oflaser material processing, comprising the steps of

-   -   a. Recording a real-time image comprising the position and        surroundings of the process during material processing by a        camera arranged in or on a laser material processing head;    -   b. Determining at least one image section in the real-time image        and its location on a camera sensor, including the determination        of        -   i. an actual position of the process in material processing,            as well as        -   ii. a nominal position of the relevant image section using a            projection of programmed path data for controlling the laser            material processing head in the section of the real-time            image; and    -   c. Transferring the at least one image section from the camera        to a computer.

The concept of determining a current position of the process in thematerial processing also includes the beginning or start of a new seam.Said beginning needs not to be exactly where it was programmed, forexample, because workpieces are slightly misplaced. In thisconstellation, however, there is still no seam or a currently ongoingprocess.

In another aspect, the method may include calculating deviations betweenfuture actual and nominal positions.

Furthermore, the offsetting of the specific deviations with theprogrammed web data is provided for the prediction of future imagesections.

It is also provided according to the invention that the to a cameratransmitted at least one image section is edited. In particular, beforethe process takes place, the intended processing comprises determinationof the exact position of an edge, perpendicular to the laser beam,determination of the exact position of an edge, along the laser beam,determination of the orientation of an edge, determination of theprofile of an edge, determination of the edge presence of contaminationor impurities around a position to be machined, determining the distancebetween the parts to be connected (e.g. distance between top and bottomplate). The term edge does not refer exclusively to the edge of theupper sheet that is to be processed, but can refer to a mark, with whichthe desired or nominal position of the laser material processing wasmarked on a workpiece.

Furthermore, the processing of image sections can take place in theprocess and then in particular to determine the size, shape and depth ofthe so-called “keyholes” (=hole, which is burned by the laser during themachining of workpieces in the material), determining the shape of theso-called “keyhole”, determining the depth of the so-called “keyhole”,determining the amount of light from the process, determining thespatial light distribution during the process, determining the amount ofdroplets emitted by the process, determining the speed of dropletsemitted by the process, determining the diameter of droplets emitted bythe process and determining a temperature profile related to theposition of laser material processing.

In addition, the processing of image sections after the process, inparticular the determination of the exact position of an attached seam,perpendicular to the laser beam determination of the exact position ofan attached seam, along the laser beam, determination of the shape ofthe produced seam, determination of the amount of pores in the producedseam, determination of the distance between top and bottom sheet afterboth have been joined, determination of surface finish immediatelyadjacent to the point being worked, determination of a temperatureprofile around the point which has been worked, determination of theprofile of at least one of the edges, if the purpose of the process wasseparation.

Also, the at least one image section of before or after the process canbe used to determine the processing speed.

In a further embodiment, the method may include the recording ofreal-time images and/or a sequence when joining or separatingworkpieces.

Furthermore, it is provided that the camera is previously calibrated,wherein the calibration may include the focus on the position of theworkpiece to be machined.

In addition, for the method according to the present invention, it maybe provided that the path data additionally has predefined points ofinterest.

It is provided in a further embodiment of the method according to theinvention that real-time images and/or the sequence of real-time imagescan be stored and/or the relevant image section and/or the sequence ofimage sections can be stored for documentation.

Furthermore, the data can be derived from a selected image section andcompared with data stored in a database. The creation of a correspondingdatabase is also a further aspect of the method according to theinvention.

It is also provided according to the invention that data is derived fromthe at least one specific image section and stored.

A further aspect of the method according to the invention relates to thecontrol of other devices by the laser material processing head based ondetermined deviations between future actual and nominal values.

The method of the present invention can also be configured so that thelaser material processing head and/or the workpiece is guided dependingon determined deviations between future actual and desired positions.Furthermore, it is also provided that the laser power is adjustedaccording to the determined deviations between the actual and nominalvalues.

Furthermore, the invention provides for the method that an actuator isset within the laser material processing head on the basis of determineddeviations between actual and nominal values.

In a further aspect, the present invention relates to a method forselecting sections from camera images, comprising the steps of

-   -   a. Recording of a real-time image and/or a sequence of real-time        images before, during or after material processing by a camera        arranged on a laser material processing head;    -   b. Projecting the path data for controlling the laser material        processing head in the material processing in the real-time        image and/or the sequence of realtime images;    -   c. Selection of at least one image section in the real-time        image and/or a sequence of real-time images;        in laser material processing.

Still other aspects, features, and advantages of the present inventionare readily apparent from the following detailed description, simply byillustrating a preferable embodiments and implementations. The presentinvention is also capable of other and different embodiments and itsseveral details can be modified in various obvious respects, all withoutdeparting from the spirit and scope of the present invention.Accordingly, the drawings and descriptions are to be regarded asillustrative in nature, and not as restrictive. Additional objects andadvantages of the invention will be set forth in part in the descriptionwhich follows and in part will be obvious from the description, or maybe learned by practice of the invention.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be described based on figures. It will be understoodthat the embodiments and aspects of the invention described in thefigures are only examples and do not limit the protective scope of theclaims in any way. The invention is defined by the claims and theirequivalents. It will be understood that features of one aspect orembodiment of the invention can be combined with a feature of adifferent aspect or aspects of other embodiments of the invention, inwhich:

FIG. 1 shows in its left part a seam to be welded (line, 1), the workingarea of the remote welding head (large rectangle, 2) and the cameraimage (small square, 5). The middle part shows the camera image (largesquare, 5), the seam to be welded (line, 1) and the image section (areaof interest, AOI, small rectangle, 10). The right part of the FIGUREshows the image section (large Square, 10), the seam to be welded (Line,1) and the center of the picture (point in the square, 12)

DETAILED DESCRIPTION OF THE INVENTION

The above-stated object of the invention is achieved by the features ofthe independent claims. The dependent claims cover further specificembodiments of the invention.

The invention provides a method by which the material processing of aworkpiece before, during or after the joining or cutting process can bemonitored or even corrected. In this case, the future position of theposition of the material processing is calculated beforehand by thecombined use of the pathe data on which the processing head is to beguided together with a section of a real-time image of the materialprocessing.

By means of the method according to the invention, it is possible tomonitor prior to the process, that is to say where welding is going totake place soon. Thus, the actual state of the nominal position of theposition of the material processing can be detected and corrected. Thus,the position of the (future) process can already be corrected and notthe current process or the current position of the material processingprocess. Time is needed for such a correction. The method according tothe invention advantageously makes it possible to look ahead a fewmillimeters (ie “into the future”). The approximate location of thefuture location can be deduced, in particular in the remote weldingprocess, from the current welding position in combination with the knowndesired position from the programmed path.

A position may also be considered at which the process itself took placewithin the meaning of that welding occurred. In this case, qualitycontrol is usually the aim. The relevant position can be deduced fromthe position where welding took place, i.e. from the data that areavailable to the remote welding head, possibly including the correctiondiscussed in the previous paragraph.

It is still possible to look at the ongoing process, i.e. the positionat which welding is currently being carried out. This variant offers thepossibilities to regulate the process itself. However, this location isalso well known, both in the real space and on the camera.

Due to the use of the planned and known path data of the laser materialprocessing head, the method of the present invention allows not only tomatch the actual state with a nominal state or accurately reproduce theposition of the process of material processing, but on the basis ofusing of previously known data for path guidance of the laser processinghead even directly upcoming events may be taken into account. Thus, theselection of the image area can already be planned in advance, whereinthe processing of the image is faster because less data due to thereduction of the pixels to be transmitted and processed. As a result,relatively complex algorithms can be used, and it is neverthelessensured to edit or determine the relevant image sections fast enough.

In the method according to the invention, the image area can be selectedfreely within the search range of a camera at runtime. In connectionwith the method according to the invention, it should be emphasized thatthe selection of the image area is accompanied by a reduction of thepixels. A calculation of the measured deviations from the programmedpath takes place and based the relevant section in the camera image ispredicted on that basis. In the method according to the invention, it isalso possible to use only the programmed path for prediction, that is tosay completely without seam guidance.

FIG. 1 shows in the left part the seam 1 to be welded, the working space2 of the remote welding head and the camera image 5. In the center ofFIG. 1, the camera image 5, the seam 1 to be welded and the relevantarea of interest (AOI) are shown. The image section 10 shows thenecessary area of the entire camera compartment 5, which is sufficientfor the method according to the invention.

In the right part of FIG. 1, the image section 10 is shown, which can beseen to be welded seam 1 and the image center 12. The image center 12corresponds to the position at which the remote welding head predictsthe seam.

The remote welding head can weld seams anywhere in its working space 2(FIG. 1, left part of the image). Also, there are no restrictions on theorientation of the seams to the workspace and thus to the remote weldhead.

The seams are preprogrammed, so the remote welding head knows the courseof the seams in the three-dimensional space. However, there may be smalldeviations in the space during processing, because the work piece has adifferent than planned, the preparation of the work piece was lessaccurate, or the welding head is differently orientated in space. Inorder to ensure that welding takes place exactly where welding shouldtake place, according to the invention, a point is considered which isto be welded in immediate proximity, i.e. a few milimeter before theposition of the actual welding process. Because this can be everywherein principle, a camera takes up the entire spatial area around theposition of the welding process (see FIG. 1, Middle).

According to the present invention, it is intended not to use the entirecamera image, since too many pixels would be included in thecalculation, making the calculation more complex resulting in morecomputing time that will be needed. Furthermore, using the entire image,many different details are seen in the image which are not relevant, andwhich may interfere with seam detection algorithms.

According to the invention, therefore, a small image section (=AoI, Areaof Interest) is selected. It is intended to weld in this image sectionat time T2. However, this is in the future, so there is still time forcorrection. Thus, already at time T1, the current time of processing, ithas to be determined where image section time T2 will lie exactly. Thisis calculated from the current (T1) position of the welding process andthe programmed path, ultimately from the course of the nominal seam.Since the determination takes place in close spatial proximity, a fewmillimeters before the position of the welding process, the deviationbetween the nominal and actual seam is small and the actual seam isstill located in the selected image section (FIG. 1, right part of theimage).

FIG. 1 and the text above describe the method of selecting a patch if itis to be used for seam tracking. A similar process can be used to lookinto the welding process itself or to take the pictures of the alreadywelded seam, e.g. for quality control. These positions can be calculatedexactly from the available data. Likewise, these methods can be appliedto other laser material processing processes, such as e.g. lasercutting.

The foregoing description of the preferred embodiment of the inventionhas been presented for purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed, and modifications and variations are possible in lightof the above teachings or may be acquired from practice of theinvention. The embodiment was chosen and described in order to explainthe principles of the invention and its practical application to enableone skilled in the art to utilize the invention in various embodimentsas are suited to the particular use contemplated. It is intended thatthe scope of the invention be defined by the claims appended hereto, andtheir equivalents. The entirety of each of the aforementioned documentsis incorporated by reference herein.

REFERENCE NUMERALS

-   1 seam (to be welded)-   2 Workspace remote welding head-   5 camera image-   10 image section-   12 image center

What is claimed is:
 1. A method of monitoring the process of lasermaterial processing, comprising the steps of: a. recording a real-timeimage comprising the position and surroundings of the process duringmaterial processing by a camera arranged in or on a laser materialprocessing head; b. determining at least one image section in thereal-time image and its location on a camera sensor, including thedetermination of: i. a current position of the process in materialprocessing; and ii. a nominal position of the relevant image sectionusing a projection of programmed path data for controlling the lasermaterial processing head in the section of the real-time image; and c.transferring the at least one image section from the camera to acomputer.
 2. The method of claim 1, comprising calculating deviationsbetween future actual and nominal positions.
 3. The method of claim 2,further comprising allocation of the determined deviations with theprogrammed orbit data for predicting future image excerpts.
 4. Themethod of claim 1, wherein the to a camera transmitted at least oneimage section is edited.
 5. The method of claim 1, wherein the at leastone image section recorded before or after the process of materialprocessing is used to determine the processing speed.
 6. The method ofclaim 1, comprising the recording of real-time images or a sequence whenjoining or separating workpieces.
 7. The method of claim 1, wherein thecamera is calibrated prior to performing the method.
 8. The method ofclaim 1, wherein the calibration comprises the focus on the position ofthe workpiece to be machined.
 9. The method of claim 1, wherein the pathdata additionally comprise predefined points of interest.
 10. The methodof claim 1, wherein the real-time images or the sequence of realtimeimages are stored.
 11. The method of claim 1, wherein the relevant imagesection and/or the sequence of image sections can be stored fordocumentation.
 12. The method of claim 1, wherein the data are derivedfrom a selected section and compared with data stored in a database. 13.The method of claim 1, wherein data are derived from the at least oneimage section and are stored.
 14. The method of claim 1, wherein thelaser material processing head controls other devices based ondetermined deviations between future actual and nominal values.
 15. Themethod of claim 1, wherein the laser material processing head and/or theworkpiece is guided depending on determined deviations between futureactual and nominal positions.
 16. The method of claim 1, wherein thelaser power is adjusted according to the determined deviations betweenthe actual and nominal values.
 17. The method of claim 1, wherein anactuator is set within the laser material processing head on the basisof determined deviations between actual and nominal values.
 18. A methodfor selecting sections from camera images, comprising the steps of a.recording of a real-time image and/or a sequence of real-time imagesbefore, during or after material processing by a camera arranged on alaser material processing head; b. projecting the path data forcontrolling the laser material processing head in the materialprocessing in the real-time image and/or the sequence of real-timeimages; c. selection of at least one image section in the real-timeimage and/or a sequence of real-time images; wherein the method isperformed in laser material processing.